Edit in JSFiddle

<hatena-bookmark
    params="url: 'http://blog.shibayan.jp/entry/20130711/1373549632'">
</hatena-bookmark>

ko.components.register("hatena-bookmark", {
    viewModel: function (params) {
        var self = this;
        
        self.title = ko.observable();
        self.url = ko.observable();
        self.bookmarks = ko.observableArray();
       
        $.ajax({
            type: "GET",
            url: "http://b.hatena.ne.jp/entry/jsonlite/",
            data: {
                url: params.url
            },
            dataType: "jsonp"
        }).done(function (result) {
            ko.mapping.fromJS(result, {}, self);
        });
    },
    template:
        '<div>\
            <h2 data-bind="text: title"></h2>\
            <p>\
                <span data-bind="text: url"></span>\
            <p>\
            <ul data-bind="foreach: bookmarks">\
                <li data-bind="visible: comment().length > 0"><span data-bind="text: user"></span> - <span data-bind="text: comment"></span></li>\
            </ul>\
        </div>'
});

ko.applyBindings();